Electro magnetic interference (EMI) generated by high frequency switch in switched-mode power supply (SMPS) voltage regulator circuit can be transmitted through AC power line in conduction or radiation manner, which effects normal working of peripheral equipments such as communication tools, household appliances, and auto control devices, etc.
For EMI control, radiation energy control standard is formulated to ensure no impact on normal working due to inter-interference among various equipments. In practice, EMI filter is often used to reduce the EMI, however, apparatuses such as external capacitor and inductor are needed which increases size and cost of PCB.